Where were enslaved Africans more desirable than Native Americans?

the native Americans were not familiar to the sicknesses that the British and Spanish brought over so when they were enslaved for a short time they were dieing faster than they could get new ones compared to the African Americans which was exposed to these sicknesses before and was better addapted to the diseases. Just a little more information the blacks or African Americans were more expensive so the use of endenshured slaves was more popular.